The long-term goals of this research project are to elucidate the molecular mechanisms of cellular adhesiveness to extracellular substrata. During the period of this project, the major emphasis will be on the adhesion of fibroblasts and the role of fibronectin in cell adhesion. A combination of biochemical, immunological and microscopic methods will be used. Studies will be carried out on the problems listed below. (1) What are the similarities and differences between baby hamster kidney (BHK) cell spreading on plasma fibronectin-coated surfaces and phagocytosis of plasma fibronectin-coated latex beads? (2) What are the identities of the BHK cell surface sites involved in cell adhesion that are blocked by antibodies directed against BHK cell wheat germ agglutinin receptors? (3) How do the synthesis, secretion and organization of fibronectin produced by human skin fibroblasts vary when cell attachment and spreading on collagen and plastic substrata are compared? (4) How does BHK cell attachment and spreading differ on plastic surfaces coated by fibronectin or serum? (5) What are the properties of the cell surface sites involved in binding of soluble fibronectin to BHK cells at 4'?